Living donor liver transplantation has rapidly gained acceptance as a treatment option for selected patients with end-stage liver disease. Over the past 5 years, LDLT has grown from approximately 50 - 60 cases per year to nearly 500 cases this year, accounting for nearly 10 % of all liver transplants performed in the United States. While reports of small series of patients have demonstrated that LDLT can be technically performed with relatively few problems, there have been no controlled studies evaluating the efficacy of this procedure compared to cadaveric transplantation. A careful evaluation of LDLT is necessary because of the potential impact of this procedure on liver transplantation. The LDLT Cohort Study is a multi-center controlled study designed to measure the outcomes of donors and recipients of LDLT. There are several important issues which the LDLT Cohort Study will address. First, a direct comparison of survival of recipients of LDLT compared to cadaveric transplantation will be made. Since selection of the LDLT recipient is different than cadaveric transplantation, the control group for this study must be carefully chosen. Second, LDLT may potentially reduce waiting list mortality by reducing waiting time prior to transplantation. In addition, there is preliminary data which suggests that LDLT recipients with hepatitis C (which is the most common indication for LDLT) may have a worse outcome compared to their cadaveric counterparts. The impact of LDLT on the donor must be evaluated. The live donor is by definition a healthy individual who undergoes a major abdominal surgery for no personal benefit. There currently are very little data on the impact of this donor surgery on the donor's survival and quality of life. Therefore, it is imperative to determine donor mortality and morbidity rates associated with LDLT. Finally, the LDLT Cohort Study provides an opportunity to directly the total cost of LDLT with cadaveric transplantation. With completion of the LDLT Cohort Study, the medical community will have a much clearer understanding of the impact of this important procedure on liver transplantation, LDLT recipients and LDLT donors.